The present disclosure relates to downhole pumps. More particularly, the present disclosure relates to downhole diaphragm pumps configured to provide improved performance over a range of flow rates encountered in unconventional wells with a resulting increase in production rates and total reservoir recovery.
Pump systems are used in a wide variety of environments, including wellbore applications for the growing market of unconventional wells. Unconventional wells, such as unconventional gas reservoirs, including coal bed methane and ultralow-permeability sand/shale, present unique challenges. Among these challenges are corrosive environments, high temperatures, large temperature differentials, high pressures and significant pressure differentials, mixed phase production of water, oil, gas and solid particulate, corrosive chemicals, unsteady flow rates, and significant declines in total production rate over time. Currently suboptimal artificial lift (AL) methods are used to produce these wells resulting in loss of production and a reduction in total recovery of the reservoirs.
Unconventional wells require special recovery operations outside the conventional operating practices. It is known to use displacement pumps for high pressure applications. In particular, diaphragm pumps provide sealing of the pressure generating elements from the production fluid by one or more diaphragms. In this type of pump, the production fluid is caused to move into and out of one or more pump sub-chambers through one or more check valves to accomplish the pumping action. There are many examples of this type pump in the patent literature, but in general they are not utilized in downhole unconventional pumping situations due to high cost and unreliability.
In the field of oil and gas, there is a strong business need for reliable efficient and flexible artificial lift devices that can operate in the harsh conditions of unconventional wells. Accordingly, it is desired to provide for a diaphragm pump for use in downhole unconventional well applications that is configured for operation in corrosive environments including high temperature environments with large temperature differentials and high pressure environments, with significant pressure differentials. In addition, it is desirable to provide for a diaphragm pump for use in the mixed phase production of water, oil, gas and solid particulate, and for use with corrosive chemicals and unsteady flow rates, without a significant decline in total production rate over time. Further, it is desired to provide for a diaphragm pump that includes tolerance to contaminants, such as sand, thus providing for an increase in the lifespan of the pump.